Having a Power of Attorney Revoked Due to Abuse?

My aunt has POA over my grandmother. After a recent yearly visit (I live in the UK and Grandmother lives in Hawaii), I noticed bruising on both my grandmother's arms. The home carer also documented the bruising. When questioned my grandmother said to the carer, to ask her daughter about it. When I asked my grandmother, she said her daughter sometimes grabs and shakes her.

I confronted my aunt and she denied causing the bruises without giving any explanation of how those bruises appeared. She has now banned me from visiting my grandmother at the house where they live, and even at her day care lodge.

My grandmother has also had very bad diarrhea and lost much weight. On inspection of the fridge that most of the food was moldy and tins of food over 2 years old. This was being fed by my aunt to my grandmother.

I have contacted the local authorities who are now investigating my complaints, but they will not give me any information with regards to progress due to not having any legal right to it.

If the local authorities do not remove POA can I apply to the courts to have the POA removed from my aunt to have it controlled by the State? What are my chances?